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Fig. 15.7
Map of annual average freezing level height (FL) in km
15.3.3.3 Freezing Level Height (FL)
Chiu and Chang (
2000
) compared the SSM/I METH freezing height (FL) with
results from general circulation models (GCMs). While there is a small bias
between the FL and the freezing level derived from GCMs in the tropics, there
are rather large discrepancies in the mid-latitudes. There is a relative weak but
significant diurnal variation of the FL as computed from the DMSP morning and
afternoon passes (Chang et al.
1995
). As pointed out earlier, FL is a columnar
moisture index. The retrieved quantity is a “rain volume”, i.e., a product of the rain
column height and the rain rate. Hence, errors in the FL will impact the rain rate
inversely. Figure
15.7
indicated the annual average FL.
15.3.3.4 Rain Frequency (
p
)
An early climatology of the METH SSM/I rain frequency (
p
) showed maxima
peaks that follows the thermal equator and at latitudes 45-50
in both hemispheres
(Chiu and Chang
1994
). Figure
15.8
shows that the equatorial and high latitude
(~50
) maxima are about 50% and there are subtropical minima (~20
latitude) of
about 30%.
Quantitative rainfall measurements were not included in the ship observations
collected in ICOADS. However, meteorological observations of precipitation were
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